Support subtitles for native fullscreen video

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 520 matching lines @@
 
     // FIXME: pseudo should be deprecated after all pseudo is replaced with ::part.
     const AtomicString& pseudo() const;
     void setPseudo(const AtomicString&);
     const AtomicString& part() const;
     void setPart(const AtomicString&);
 
     LayoutSize minimumSizeForResizing() const;
     void setMinimumSizeForResizing(const LayoutSize&);
 
-    virtual void didBecomeFullscreenElement() { }
-    virtual void willStopBeingFullscreenElement() { }
+    virtual void didBecomeFullscreenElement();
+    virtual void willStopBeingFullscreenElement();
 
     bool isFinishedParsingChildren() const { return isParsingChildrenFinished(); }
     virtual void finishParsingChildren();
     virtual void beginParsingChildren() OVERRIDE FINAL;
 
     PseudoElement* pseudoElement(PseudoId) const;
     RenderObject* pseudoElementRenderer(PseudoId) const;
 
     virtual bool matchesReadOnlyPseudoClass() const { return false; }
     virtual bool matchesReadWritePseudoClass() const { return false; }
@@ skipping 535 matching lines @@
 
 inline const Attribute* ElementData::attributeItem(unsigned index) const
 {
     RELEASE_ASSERT(index < length());
     return attributeBase() + index;
 }
 
 } // namespace
 
 #endif